[Feat] Support reconvert image from nydus to oci

[basuotian]

Feat: https://github.com/dragonflyoss/nydus/issues/1682

The current implement is very rough as some logic should be changed in "github.com/containerd/containerd/v2/core/images/converter". (see unit test testImageReConvertBasic)

Please take a look and see if is necessary to open a pr to containerd.

[imeoer]

@basuotian Thanks for the PR! How about moving the containerdreconverter codes into a forked nydus-snapshotter repo? This way we can clearly see the diff of the changes. :)

[basuotian]

@basuotian Thanks for the PR! How about moving the containerdreconverter codes into a forked nydus-snapshotter repo? This way we can clearly see the diff of the changes. :)

OK, I did move containerdreconverter into repo github.com/basuotian/nydus-snapshotter-reconverter, and these codes should be part of github.com/containerd/containerd/v2/core/images. @imeoer PTAL

[basuotian]

@BraveY Thanks for review, fixed follow your recommendations, PTAL

[BraveY]

@basuotian Thanks for the PR! Have you modified the code related to the nydusify convert command? Nydusify also needs to support the reconvert feature. Maybe @Zephyr could help implement this.

[basuotian]

@basuotian Thanks for the PR! Have you modified the code related to the nydusify convert command? Nydusify also needs to support the reconvert features. Maybe @zephyr could help implement this.

Yes, i have already finished the code in nydusify, as nydusify depends on nydus-snapshotter so this pr run first

[BraveY]

Thanks, Others LGTM! @imeoer cc

[BraveY]

@basuotian hi would you fix the broken lint CI? thanks!